This project proposes to investigate the event-related potential (ERP) correlates of information processing in two age categories of attention deficit disordered, learning disabled, and normal children. Specifically, two experimental paradigms, modeled after Ford et al. (l979) and Courchesne (l978), will be employed to examine the effects of one short-term memory scanning and one attention paradigm on subjects' P3 components and reaction times. Subjects will be assigned to groups based upon scores on psychological (WISC-R) and achievement (WRAT) tests, teacher questionnaires (Conners' index), and clinical evaluations. In addition, they will be administered a developmental neurological evaluation by the project psychiatrist. Trials in the short-term memory task will consist of a memory set (one, three, or five stimuli) a warning tone and a probe (recall) stimulus. ERPs and reaction times will be calculated for each memory set size and whether the probe was in or out of set. The attention paradigm will consist of four visual classes of events (an infrequent "target" letter sequence, a frequent "background" letter sequence, novel visual patterns and familiar 3 letter words) and one auditory event (800 Hz tone) in two sessions. ERPs will be calculated for each visual class in each session. ERP data will be analyzed using base to peak measures and principle component analyses. RT, performance, and neurological examination data will also be analyzed and correlated with ERP peaks. ERP amplitude and ERP and RT latency differences are hypothesized between groups, as is a better understanding of the electrocortical correlates of information processing in these children.